We have demonstrated that delta9 tetrahydrocannabinol (pi delta9THC), the major psychoactive ingredient of marijuana, causes a unique behavioral effect (convulsions) in a specially bred colony of rabbit. This convulsive trait is inherited, presumably by a single autosomal recessive mechanism, in these University of Arizona tetrahydrocannabinol seizure susceptible (SS) rabbits. The minimal intravenous (i.v.) dose of (delta9THC for rabbit convulsions (.05 mg/kg) is comparable to the reported minimal i.v. dose of delta9THC for human psychoactivity. Moreover, marijuana cannabinoids that are known to be psychoactive in humans (e.g., Nabilone, 11-hydroxy delta9THC, delta8THC, delta6 alphaTHC, cannabinol) cause convulsions in our SS rabbits at comparable doses. Human non-psychoactive cannabinoids (e.g., cannabidiol, cannabidiol dimethyl ether, 8-alpha-hydroxy delta9THC, cannabichromine, etc) do not cause rabbit convulsions even at high doses (10-20 mg/kg, i.v.). Further, delta9THC does no produce convulsions in other populations of "normal" or non-delta9THC seizure susceptible (NSS) rabbits (10-29mg/kg, i.v.) or for that matter, in any animal species that have been tested. Also, non-cannabinoid hallucinogens (e.g., LSD, mescaline, phencyclidine, psilocybin, methamphetamine, etc.) do not cause convulsions in SS rabbits. Tolerance to, and cross-tolerance between, delta9THC and cannabinol occurs. These data suggest that the SS rabbit represents a unique laboratory animal model of marijuana induced psychoactivity in humans. Additional studies are underway to ascertain the effects, loci, and mechanisms of action of the psychoactive cannabinoids in SS rabbits.